A bogus hijack threat grounded a JFK-bound American Airlines jet right before takeoff yesterday in San Francisco, forcing passengers to sit aboard the craft for several hours before being searched, a source said.

The FBI determined the phoned-in threat, which was made to a clerk at a San Francisco-area business, wasn’t credible.

Two passengers, who a witness said was a couple with Pakistani passports, were removed in handcuffs and questioned, but later released.

“A flight attendant or a member of the crew or another passenger . . . dropped the dime on them,” an FBI source said.

Flight 24, scheduled to take off at 7:30 a.m. from San Francisco, was grounded at 10 a.m.